2 Effects of Oxygen and other Gases 



of an air which, in its duly mixed state, possesses such a direct 

 property of maintaining the vital principle — a properly not 

 belonging to any other substance. 



Vjirious opinions have been offered upon this subject ; and 

 experirpental inquiries, both of a chemical and physiological 

 kind, have frequently been instituted at different periods. But 

 the results of these do not appear to be sufficiently satisfactory 

 to set the question at rest. I am, therefore, disposed to draw 

 attention to some experiments which 1 have made myself, and 

 which appear to disclose facts leading to an explanation some- 

 what different from those hitherto received, as far as relates to 

 the physiology of this subject, the chemical ground being satis- 

 factorily occupied. 



These experiments were commenced in the year 1827 ; anct^ 

 appearing to afford conclusions opposite to those usually undisr- 

 stood, they were renewed in the course of 1828, and farther 

 prosecuted at the beginning of the last year, with the assistance 

 of Mr. George Wood, Mr. Miles, Mr. Ferguson, Mr. Murray^ 

 and others, well accustomed to the management of pneumatic 

 chemistry, and conversant with experimental physiology. The 

 gas itself was generally made by exposing black oxide of man- 

 ganese to the red heat of an iron crucible, and tested with a 

 taper previous to every experiment. Glass jars were inverted 

 upon the shelf of a water- bath, and on this a raised platform 

 supported the animal above the level of the surrounding water. 

 During the severe frosty weather, the bath was kept clos^ 

 to a large fire, and the water was otherwise preserved at an 

 elevated temperature. The animals were passed quickly and 

 carefully through the water into the gas, which was previously 

 collected by a metallic worm, communicating between the bath 

 and the heated crucible ; and these, and all the other delicate 

 operations necessary, were very adroitly performed by my intel- 

 ligent assistants. As a preliminary step, some kittens, mice, 

 and sparrows, were placed under glass jars of atmospheric air, 

 and the duration of their lives was compared with that of others 

 immersed in like quantities of oxygen : the result of which 

 comparative experiment was this — that the animals died muck 

 sooner in the jars of common air than in those of unmixed 

 oxygen. And, when the gas was tested, after the removal of 

 the animals frona the atmospheric air^ it evinced the presence 



